Embodiments described herein relate to a hydrocarbon trap having improved adsorption of emissions, and more particularly, to a hydrocarbon trap including a high porosity carrier material in the form of a flow-through substrate which allows a large loading of zeolite to provide improved adsorption of hydrocarbons.
In recent years, considerable efforts have been made to reduce the level of hydrocarbon (HC) emissions from vehicle engines. Conventional exhaust treatment catalysts such as three-way catalysts achieve conversion of hydrocarbons to water and help prevent the exit of unburnt or partially burnt hydrocarbon emissions from a vehicle. However, hydrocarbon emissions are high during cold starting of the engine before the latent heat of the exhaust gas heats the catalyst and allows it to become active, i.e., before the catalyst has reached its “light-off” temperature.
Hydrocarbon traps have been developed for reducing emissions during cold-start by trapping/adsorbing hydrocarbon (HC) emissions at low temperatures and releasing/desorbing them from the trap at sufficiently elevated temperatures for oxidation over a catalyst, such as a three-way catalyst. The HC traps are positioned in the exhaust gas stream of a vehicle. Currently, zeolites have been the most widely used adsorption materials for hydrocarbon traps. The zeolites are typically combined with a three-way catalyst in the form of a washcoat which is supported on a monolithic substrate.
While increasing the zeolite washcoat loading typically provides improved conversion efficiency, there is a limit to how much the total washcoat loading can be increased without experiencing decreased conversion efficiency and an undesirable increase in backpressure in the HC trap.
It would be desirable to improve the overall HC trap function by maximizing hydrocarbon adsorption capacity during cold starts and minimizing the desorption rate of hydrocarbons from the trap until the catalyst has reached its “light off” temperature.